1. Field of the Invention
This invention relates to a laser beam recording system, and more particularly to an improvement in a system of recording characters by a laser beam scanning device.
2. Description of the Prior Art
The laser beam recording device or scanning device referred to in this application means a device which uses a laser beam as a light source and modulates the laser beam by a character signal and causes the laser beam scan on a recording material in a main scanning direction and a sub-scanning direction to record characters and/or marks in a dot pattern. As the examples which use the laser beam recording device are known press facsimile, remote sensing image recording device, COM (computer output microfilmer), type photo-composing machine, printing plate exposure device, video disc master recording device, data recording device, etc.
The reason for using a laser beam as the light source is mainly the high energy and high concentration it has and accordingly is in that the recording can be conducted at a high speed with high density on a low sensitive recording material. As the low sensitivity recording material, are known so-called heat mode recording materials having a recording layer of a single or multi-layer of metal, semi-metal or non-metal like a semi-conductor or a layer of vacuum deposition of alloy. These low sensitive recording materials are advantageous in that no developing process is needed and the recording process can be conducted in a bright room or under bright safety light.
However, when a laser beam recording is conducted on the low sensitive recording material of heat mode type, the dots recorded on the material constitute a character "E" in FIG. 1 fat in the direction perpendicular to the main scanning direction (sub-scanning direction) of the laser beam. Since the character recorded is constituted of a number of elements of dots of square shape, the fatting in the sub-scanning direction makes the shape of the character deformed and illegible. This phenomenon is considered to be based on the excessive energy of the scanning laser beam spreading in the sub-scanning direction. The degree of the fatting has been proved as a result of tests to be from about 10% to about 100% of the width of the dots depending on the material used.